In order to sense fire occurrence or gas leakage in a large space such as an inside/outside of a ship and an inside/outside of a plant or a building, a smoke sensor for sensing smoke generation, a temperature sensor for sensing surrounding temperatures, a flame sensor for sensing flame generation, etc. have been installed, and thus a system for detecting the fire occurrence or gas leakage according to the operation of the respective sensors has been used.
As an example of such a system, Korean Patent No. 1311950 (Sep. 17, 2013) entitled a fire and gas detection system having a bidirectional communication loop is disclosed (hereinafter, referred to as the conventional art).
According to the conventional art the fire and gas detection system including: a communication loop including (+) line to which an operating voltage and a digital call signal are supplied and (−) line which is arranged in parallel to the (+) line; a fire detecting sensor which is connected to the communication loop, and analyzes the digital call signal and transmits a measurement value in the form of a current signal, at the time when the fire detecting sensor itself is called; an interface unit which includes a loop A terminal and a loop B terminal, applies the operating voltage and the digital call signal to the (+) line, and receives the current signal outputted by the fire detecting sensor from the (−) line; and a main control panel which is connected to the interface unit, provides the digital call signal, and receives the measurement value from the called fire detecting sensor and then processes the measurement value according to a pre-inputted program, is disclosed.
However, even in case where such a bidirectional communication loop is used, in a dangerous region in which a disaster occurrence possibility is relatively high, sensors are arranged in parallel between (+) line and (−) line and a single direction communication not a bidirectional communication is used. If such a single direction communication is used, in case within a dangerous region the (+) line and the (−) line melt and stick together by heat or flame to be shorted as a result of fire occurrence and gas leak within a dangerous region, power supply function and power line communication function through the lines both become impossible.
Hence, there is a need for a new technology for handling the short of the (+) line and the (−) line as well as the disconnection of one of the (+) line and the (−) line disclosed in the conventional invention.